The top American military officer, General Peter Pace, declined Monday to endorse the conclusions of U.S. military officers in Baghdad, who told reporters on Sunday that the Iranian government is providing high-powered roadside bombs to insurgents in Iraq. General Pace made his comments during a visit to Australia, and VOA's Al Pessin reports from Canberra.

General Pace said he was not aware of the Baghdad briefing, and that he could not, from his own knowledge, repeat the assertion made there that the elite Quds brigade of Iran's Republican Guard force is providing bomb-making kits to Iraqi Shiite insurgents.

"We know that the explosively formed projectiles are manufactured in Iran. What I would not say is that the Iranian government, per se [specifically], knows about this," he said. "It is clear that Iranians are involved, and it's clear that materials from Iran are involved, but I would not say by what I know that the Iranian government clearly knows or is complicit."

Military officers who spoke to reporters in Baghdad, Monday, on condition of anonymity, said the high-powered projectile bombs are made with parts manufactured in Iran and that intelligence indicates the parts are sent to Iraq with the approval of senior Iranian officials. The officials said the bombs, whose projectiles can pierce the skin of an armored vehicle, have killed 170 American troops.

General Pace also commented on an issue that has received a lot of attention in recent hours - the question of whether setting a specific timeline for a U.S. withdrawal from Iraq is a good idea. He says a withdrawal before Iraq's government and military can maintain stability would be disastrous and would have a 'spillover' effect in Afghanistan and elsewhere. The general commented shortly after meeting with Australian Prime Minister John Howard, but without specific reference to Howard's long-distance dispute with U.S. presidential contender Barack Obama.

"I don't see precise timelines as being useful. It should not be an open-ended commitment. Certainly it's time for the Iraqis, as they are, to stand up and take on more of their own responsibility. But to put a precise timeline on it means that you are signaling to your potential enemies that, if they just hold their breath for this amount of time, then we'll all be gone and they can come back out of the woodwork."

The latest person to enter the race to become the Democratic Party's presidential candidate next year, Senator Obama, has called for a withdrawal of all American troops from Iraq by March of next year. The Australian prime minister said terrorists would support such a plan. From around the world, Obama shot back that, if Howard feels so strongly, he should send 20,000 more Australian troops to Iraq.

Australia has just 1,400 troops in Iraq, and its entire active duty military is only 52,000 strong. But General Pace told reporters Monday the Australian troops are making a valuable contribution, in spite of their low numbers.

"The fight we're in against terrorism is not about large armies versus large armies. It's about small groups of individuals - five, 10, 15, 20 - who are reaching out to assist those who are in need," he said. "And, in that regard, both in Iraq and Afghanistan, Australia should be able to take great pride."

The general says all nations that value freedom should participate in fighting the global terrorist threat.